Giancarlo Fisichella reckons Renault need to leave no stone unturned in order to bounce back from their disappointing start to the season in Australia.

The French squad, world champions for the past two seasons, kicked off their title defence with a distant fifth place by Fisichella, who was unable to match the pace of the leading trio formed by Ferrari, McLaren and BMW Sauber.

Fisichella reckons the R27 car will need a lot more than a quick fix in order to allow Renault to compete at the top of the field.

"I wouldn't leave any stone unturned, we need to work massively on the design and on the front of the car," Fisichella told Autosprint in an interview. "With patches you don't go very far.

"We'd need something that changes the car radically. At Renault they know exactly what to do, they are working on it night and day, but it's a solution that may take a long time to come.

"So, in the next races, we'll just try to limit the damages by working on the aerodynamic appendages and on the set-up, but it won't be much."

The Roman, who finished over a minute behind race winner Kimi Raikkonen in Australia, believes the R27 has both aerodynamical and mechanical problems that need to be solved.

"With regards to the work the team did on the track, I'd say nothing, because the car has a good set-up, it's well balanced, we know what to do and how to set it up to make it work best," he added.

"It's a different matter as far as the project's aerodynamics and mechanics are concerned. It's obvious the move from Michelin to Bridgestone for us has been more difficult than for McLaren, for example.

"In Melbourne the gap to Ferrari in the race was almost embarrassing, 1.6 seconds from Raikkonen, but there was also half a second from McLaren. That is unacceptable."

The switch from Michelin to Bridgestone tyres this season seems to have hurt Renault more than their main rivals, and Fisichella admits he misses their collaboration with the French tyre supplier.

"Very much, there's no point denying it. The continuity and the collaboration we had with them brought Renault two world championships.

"Now, by contrast, we haven't been able to interpret the new car's design based on the needs of the Bridgestone tyres, while Ferrari have and to a lesser extent McLaren have as well."

With only one tyre supplier, and with engine development frozen during the season, Fisichella is concerned Renault will have a tougher time catching up with their rivals.

"Absolutely, that's why I'm worried," he said. "The areas to work on are few, that's why it's maybe better to make radical changes, even though they may be more complex and take longer.

"Since I came back to Renault, we were always top players in Australia, while this is the least performing Renault I've driven."

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